نوع مقاله : مقاله پژوهشی

نویسندگان

1 گروه زراعت، دانشکده کشاورزی، دانشگاه آزاد اسلامی، واحد گرگان، گرگان، ایران

2 گروه زراعت، دانشکده کشاورزی، دانشگاه علوم کشاورزی و منابع طبیعی گرگان، گرگان، ایران

3 گروه مهندس ژنتیک و ایمنی زیستی، پژوهشگاه بیوتکنولوژی کشاورزی، کرج، ایران

چکیده

سابقه و هدف:
ارزیابی محیط‌زیستی چرخه زندگی گیاهان زراعی در سامانه‌های تولید یکی از روش‌های مورد قبول برای دستیابی به هدف ­های کشاورزی پایدار است. بخش کشاورزی نیز سهم ‌بسزایی در انتشار گازهای گلخانه‌ای و گرمایش جهانی دارد. از این‌رو، بهبود عملیات کشاورزی ‌بعنوان راه‌کار مناسب برای تخفیف اثر­های تغییر اقلیم مطرح است. بنابراین، این پژوهش با هدف ارزیابی محیط‌ زیستی سناریوهای مختلف تولید ارقام اصلاح شده برنج اجرا شد.
مواد و روش‌ها:
پس از ارزیابی اولیه و مشورت با متخصصان برنج، 100 مزرعه در روش کاشت نیمه‌مکانیزه و 100 مزرعه در روش سنتی در منطقه ساری در سال‌های 1395 و 1396 انتخاب شدند. پس از ثبت اطلاعات، هر روش کاشت بر اساس شیوه مدیریت زراعی و مصرف نهاده‌ها به چهار نظام کاشت تبدیل شده که در مجموع هشت سناریو را تشکیل دادند. چهار سناریوی روش نیمه‌مکانیزه شامل چهار نظام کم‌نهاده (SL)1، حفاظتی (SCI)2، رایج منطقه (SCII)3 و پرنهاده (SH)4 و چهار سناریوی روش سنتی نز به‌ترتیب نظام‌های کم‌نهاده (TL)5، حفاظتی (TCI)6، رایج منطقه (TCII)7 و پرنهاده (TH)8 بودند.
نتایج و بحث:
یافته‌ها نشان داد میانگین عملکرد شلتوک در هشت سناریو برابر 6418 کیلوگرم در هکتار و میانگین انرژی ورودی در هشت سناریو برابر 93/28138 مگاژول در هکتار بود که 44/45 درصد انرژی تجدیدپذیر و 56/54 درصد انرژی تجدیدناپذیر را شامل می­شد. بیشترین انرژی ورودی در سناریوی SH و TH مشاهده شد که مربوط به نظام کاشت پرنهاده در هر دو روش کاشت است. میانگین انرژی خروجی در هشت سناریو برابر 197076 مگاژول در هکتار و بیشترین‌ انرژی خروجی در سناریوهای SCII، SH، TCII و TH به­دست آمد. میانگین بهره‌وری انرژی در هشت سناریو برابر 23/0 کیلوگرم بر مگاژول بود که کمترین میزان آن در هر دو روش کاشت در نظام پرنهاده حاصل شد و دیگر سناریوها در یک سطح قرار گرفتند. میانگین انتشار دی‌اکسید کربن در هشت سناریو برابر 37/1120 کیلوگرم معادل CO2 در هکتار بود که بذر، سوخت و ادوات و ماشین‌آلات بالاترین سهم را داشتند. از نظر پتانسیل گرمایش جهانی در واحد سطح سناریوی TH در رتبه اول و سناریوی SH در رتبه دوم قرار گرفت. بالاترین پتانسیل گرمایش جهانی در واحد وزن شلتوک و انرژی ورودی در سناریوی SL و TL به‌دست آمد. بیشترین انتشار فلزهای سنگین در آب و خاک در هر دو روش کاشت در نظام کاشت پرنهاده مشاهده شد و نظام کاشت رایج در رتبه دوم قرار گرفت. بیشترین بهره‌وری خالص اولیه (NPP)9 در سناریوهای تولید مربوط به نظام‌های کاشت رایج و پرنهاده بود که میزان آن در روش کاشت نیمه‌مکانیزه بالاتر از روش سنتی به ­دست آمد. در هر دو روش کاشت، بیشترین ورودی کربن نسبی (Ri) در سناریوهای تولید مربوط به نظام کاشت کم‌نهاده (SL و TL) حاصل شد. با توجه به کربن ورودی – خروجی و کربن خالص در هشت سناریو، میانگین شاخص پایداری نیز برابر 66/4 به‌دست آمد. بالاترین شاخص پایداری در سناریوی SCI (05/5) مشاهده شد که مربوط به نظام کاشت حفاظتی بود. سناریوهای TL، SL، SCII و TCI از نظر شاخص پایداری در رتبه‌های بعدی قرار گرفتند. در واقع، شیوه صحیح مدیریت مزرعه در نظام تولید حفاظتی به کاهش انتشار آلاینده‌های محیط‌زیستی منجر شد.
نتیجه‌گیری:
طبق یافته‌ها، نظام‌های کاشت کم‌نهاده و حفاظتی در هر دو روش کاشت به شاخص‌های توسعه پایدار نزدیکتر بودند. همچنین، کشاورزان منطقه در نظام‌های تولید پرنهاده و رایج بیشتر، بهره‌وری اقتصادی در تولید برنج را در نظر گرفته و کمتر به پایداری محیط‌زیستی و بهره‌وری انرژی توجه داشتند. از این‌رو، استفاده از یافته‌های این پژوهش می‌تواند برای افزایش پایداری بوم‌نظام‌ها و همچنین کاهش اثرهای سوء محیط‌زیستی ناشی از مصرف نهاده‌های شیمیایی و دستیابی به هدف ­های کشاورزی پایدار بسیار تأثیرگذار باشد.

کلیدواژه‌ها

عنوان مقاله [English]

Assessment of energy flow, carbon saving, and greenhouse gas emission in rice production scenarios

نویسندگان [English]

  • Mohammad Hosein Torabi 1
  • Afshin Soltani 2
  • Salman Dastan 3
  • Hosein Ajam Norouzi 1

1 Department of Agronomy, Faculty of Agriculture, Islamic Azad University, Gorgan Branch, Gorgan, Iran

2 Department of Agronomy, Faculty of Agriculture, Gorgan University of Agricultural Sciences and Natural Resources, Gorgan, Iran

3 Department of Genetic Engineering and Biodafety, Agricultural Biotechnology Research Institute of Iran, Karaj, Iran

چکیده [English]

Introduction:
Environmental assessment of the life cycle of crops in production systems is an accepted method for achieving agricultural sustainability. Moreover, the agricultural sector has a significant contribution to greenhouse gas emissions and global warming. Hence, improving agricultural operations is an appropriate way to mitigate the effects of climate change. Therefore, the aim of this research was the environmental assessment of different scenarios of the production of improved rice cultivars.
Material and methods:
After preliminary evaluation and consultation with rice specialists, 100 paddy fields were selected for semi-mechanized planting method and 100 paddy fields for traditional planting method in Sari region from 2015 to 2016. After recording the data, each planting method was converted into four planting systems based on agronomic management and input consumption, which formed a total of eight scenarios. Four scenarios of the semi-mechanized method were systems of low-input (SL), conservation (SCI), conventional (SCII) and high-input (SH). Four scenarios of the traditional method were systems of low-input (TL), conservation (TCI), conventional (TCII) and high-input (TH).
Results and discussion:
The results indicated that the average paddy yield in eight scenarios was 6418 kg.ha-1. The average input energy in eight scenarios was 28138.93 MJ.ha-1, which contained 45.44% renewable (biologic) energy and 54.56% non-renewable (industrial) energy. The highest input energy was observed in scenarios IV and VIII, which was related to the SH in both planting methods. The average output energy in eight scenarios was equal to 197076 MJ.ha-1. The highest output energy was obtained in scenarios III, IV, VII and VIII. The average energy productivity in the eight scenarios was equal to 0.23 kg.MJ-1 that the least amount was obtained in both planting methods and the other scenarios were on the same level. The average CO2 emissions in all eight scenarios were 1120.37 kg CO2.eq ha-1, which had the highest share related to seed, fuel, and machinery. In terms of global warming potential per unit area, scenario VIII was ranked first and scenario IV ranked second. The highest global warming potential per grain weight and GWP per input energy were achieved in scenarios I and V. The highest heavy metal emission into water and soil was observed in the SH and SCII, respectively. The highest net primary productivity (NPP) in production scenarios was related to SCII and SH, which was higher in the semi-mechanized method than the traditional method. In both planting methods, the most relative carbon inputs (Ri) were obtained in scenarios of the SH (I and V). With regard to input-output carbon and net carbon in eight scenarios, the average sustainability index was 4.66. The highest sustainability index was observed in scenario II (5.05), which was related to the conservation system. The scenarios V, I, III and VI were next ranked in terms of the sustainability index. In fact, the correct management of the paddy field in the SCI has led to a reduction in emissions of environmental pollutants.
Conclusion:
According to the findings, SL and SCI were closer to sustainable development indicators in both methods. Furthermore, the economic efficiency of rice production was more important to farmers than environmental sustainability and energy efficiency. Hence, using the findings of this research can be very effective in increasing environmental sustainability and reducing the environmental impacts of chemical inputs and achieving agricultural sustainability.

کلیدواژه‌ها [English]

  • climate change
  • Environmental pollutant
  • Greenhouse gas emissions
  • Planting system
  • Rice

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